Concept naming convention is lower case natural naming with spaces, when necessary captials should be used, for example disease factor, HIV, breast carcinoma, Ewing's sarcoma An experimental factor in Array Express which are essentially the variable aspects of an experiment design which can be used to describe an experiment, or set of experiments, in an increasingly detailed manner. This upper level class is really used to give a root class from which applications can rely on and not be tied to upper ontology classses which do change.

An experimental factor in Array Express which are essentially the variable aspects of an experiment design which can be used to describe an experiment, or set of experiments, in an increasingly detailed manner. This upper level class is really used to give a root class from which applications can rely on and not be tied to upper ontology classses which do change.